Method and apparatus for underfill of bumped or raised die

ABSTRACT

A method and apparatus for attaching a semiconductor device to a substrate. One end of the substrate is elevated to position the substrate and the coupled semiconductor device on an inclined plane. An underfill material is introduced along a wall of the semiconductor device located at the elevated end of the inclined substrate with the underfill material being placed between the substrate and the semiconductor device. An optional but preferred additional step of the invention includes coupling a barrier means to the substrate at a point on the substrate adjacent to a sidewall of the semiconductor device located at the lowest point of the slope created by the inclined substrate. The barrier means prevents the underfill material from spreading beyond the sidewalls of the semiconductor device, particularly in instances where the substrate is inclined at a steep angle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for underfillinga semiconductor device. More specifically, the present invention relatesto a method and apparatus for uniformly underfilling a bumped or raisedsemiconductor chip to be essentially void free.

2. State of the Prior Art

Flip-chip and bumped die technology is well known in the art. Aflip-chip or bumped (raised) die is a semiconductor chip (die) havingbumps on the bond pads formed on the active circuit or front sidethereof, the bumps being used as electrical and mechanical connectors,which is inverted (flipped) and bonded to a substrate by means of thebumps. Several materials are typically used to form the bumps on thedie, such as conductive polymers, solder, etc. Typically, if the bumpsare solder bumps, the solder bumps are reflowed to form a solder jointbetween the so-called flip-chip and the substrate, the solder jointforming both electrical and mechanical connections between the flip-chipand substrate. In any event, due to the presence of the bumps on theflip-chip, a gap exists between the substrate and the bottom surface ofthe flip-chip.

Typically, since the flip-chip and the substrate have differentcoefficients of thermal expansion and operate at different temperaturesand also have different mechanical properties with differing attendantreactions to mechanical loading and stresses, stress develops in thejoints formed by the bumps between the flip-chip and substrate.Therefore, the bumps must be sufficiently robust to withstand suchstressful conditions to maintain the joint between the flip-chip and thesubstrate. To enhance the joint integrity formed by the bumps locatedbetween the flip-chip and the substrate, an underfill material comprisedof a suitable polymer is introduced in the gap between the flip-chip andthe substrate. The underfill also serves to equalize stress placed onthe flip-chip and substrate, helps transfer heat from the flip-chip andhelps protect the bump connections located between the flip-chip and thesubstrate from contaminants such as moisture, chemicals, andcontaminating ions.

In practice, the underfill material is typically dispensed into the gapbetween the flip-chip and the substrate by injecting the underfill alongtwo or more sides of the flip-chip with the underfill material flowing,usually by capillary action, to fill the gap. For example, U.S. Pat. No.5,218,234 to Thompson et al. discloses a semiconductor device assemblywhereby an epoxy underfill is accomplished by applying the epoxy aroundthe perimeter of the flip-chip mounted on the substrate and allowing theepoxy to flow underneath the chip. Alternatively, the underfill can beaccomplished by backfilling the gap between the flip-chip and thesubstrate through a hole in the substrate beneath the chip.

However, the traditional method of underfilling by way of capillaryaction has a serious disadvantage. The small gap formed between theflip-chip and substrate to which it is connected prevents filling thegap in a uniform manner. Such non-uniform underfilling is particularlyprevalent in the areas surrounding the bumps interconnecting theflip-chip to the substrate. When underfilling a flip-chip on a substratesituated in a substantially horizontal plane, the underfill materialwill generally be non-uniform in character and contain bubbles, airpockets, or voids therein. This non-uniform underfill decreases theunderfill material's ability to protect the interconnections between theflip-chip and substrate and environmentally compromises the flip-chipitself, thereby leading to a reduction in the reliability of the chip.

A different method of bonding a semiconductor chip to a substrate isdisclosed in U.S. Pat. No. 5,385,869 to Liu et al. whereby the gapbetween the semiconductor chip and substrate is underfilled utilizing asubstrate having a through hole formed therein which is centrallylocated below the semiconductor chip mounted thereon. The through holehas gates or notches formed at each corner thereof which extend beyondthe semiconductor chip, which is mounted thereover. Underfilling the gapbetween the semiconductor chip and the substrate is accomplished byblocking one side of the through hole, applying an encapsulationmaterial on top of and around the chip, and allowing the encapsulationmaterial to flow into the through hole by way of the gates or notches inthe substrate.

As disclosed in U.S. Pat. No. 5,203,076 to Banerji et al., a vacuumchamber is used to underfill the gap between a semiconductor chip and asubstrate. A bead of underfill polymeric material is provided on thesubstrate about the periphery of the chip. Next, the semiconductor chipand substrate are placed within a vacuum chamber with a vacuum beingsubsequently applied to the chip and the substrate to evacuate the gaptherebetween. Air is then slowly allowed to re-enter the vacuum chamberto force the underfill material into the gap between the semiconductorchip and the substrate.

Although the underfill methods disclosed in the Liu and Banerji patentsattempt to address the problem of underfilling in a non-uniform manner,those references present solutions that require specialized substrates,use additional equipment in the underfilling process and increase thecost of production. For example, implementation of the underfillingmethod illustrated in the Liu reference requires the use of aspecialized substrate having a through hole therein. Similarly, theunderfilling method illustrated in the Banerji et al. reference requiresthe use of specialized equipment in the form of a vacuum chamber.

Therefore, it would be advantageous to develop a method for performingunderfill of semiconductor chips which results in underfill materialthat is uniform and substantially free of voids or air. It would be afurther improvement to develop a method for performing uniformunderfilling of the gap between the flip-chip and substrate that is costeffective and utilizes standard substrates.

SUMMARY OF THE INVENTION

The present invention is directed to an improved method and apparatusfor underfilling the gap between a semiconductor device (flip-chip) andsubstrate. The improved method of attaching a semiconductor device to asubstrate begins with the step of electrically connecting thesemiconductor device to the substrate. Next, one end of the substrate iselevated to a position where the substrate and semiconductor device arelocated on an inclined or tilted plane. Finally, an underfill materialis introduced along the sidewall of the semiconductor device located atthe elevated end of the inclined substrate with the underfill flowinginto and filling the gap formed between the substrate and thesemiconductor device.

The improved method of the present invention may include the step ofusing a suitable dam or barrier located adjacent to the lower edge ofthe inclined substrate, the lowest point of the inclined substrate. Thesuitable dam or barrier prevents the underfill material from spreadingbeyond the sidewalls of the semiconductor device, particularly ininstances where the substrate is inclined at a steep angle with respectto a horizontal plane.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages, as well as other novel and important features of thepresent invention will be better understood when the followingdescription is read along with the accompanying drawings of which:

FIG. 1 is a cross-sectional view of a preferred underfill dispensingstep for a semiconductor device, a bumped flip-chip, and an inclinedsubstrate in accordance with the present invention;

FIG. 2 is a cross-sectional view of another preferred underfilldispensing method, which illustrates the placement of a dam or suitablebarrier, a fence, located adjacent the substrate;

FIG. 3 is a side view illustrating the placement of the semiconductordevice, bumped flip-chip, and substrate of FIG. 1 on top of a supportmember having a vibrator attached thereto;

FIG. 4 is a top view of a semiconductor device, bumped flip-chip, and aninclined substrate illustrating the use of two suitable barriers, damsor fences, to perform the underfill step;

FIG. 5 is a cross-sectional view of another embodiment of the presentinvention, illustrating a backfill method of underfilling the gap formedbetween a semiconductor device, bumped flip-chip, and a substrate,

FIG. 6 is a cross-sectional view of another embodiment of the presentinvention, illustrating a backfill method of underfilling the gap formedbetween a semiconductor device, a bumped flip-chip, and a substratewithout the use of dams, and

FIG. 7 is a cross-sectional view of another embodiment of the presentinvention, illustrating a backfill method of underfilling the gap formedbetween a semiconductor device, a bumped flip-chip, and a substratewherein the substrate is inverted during the underfilling process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a substrate or chip carrier 10 is shown forconnecting a semiconductor device or flip-chip 12 by conventional directchip bonding techniques. Substrate 10 is typically made of ceramic,silicone, glass, and combinations thereof. Substrate 10 is preferablycomprised of a printed circuit board (PCB) or other carrier, which isused in flip-chip technology, such as an FR4 PCB. Substrate 10 has afront end 14, a rear end 16, and a top surface 18, the top surface 18having contact pads thereon.

Flip-chip 12 has a front sidewall 30, a rear sidewall 32, and an activesurface 20. The active surface 20 comprises integrated circuitry and aplurality of contact pads 22. The contact pads 22 have bumps 24 thereon,which provide both electrical and mechanical connection to substrate 10.

An electrical assembly is produced by placing and securing the flip-chip12 on the top surface 18 of substrate 10 having active circuitrythereon. Specifically, the bumps 24 are aligned with the contact pads ofthe active circuitry located on top surface 18 of substrate 10. Theflip-chip 12 is then electrically and mechanically connected to thesubstrate 10 by curing or reflowing the bumps 24, depending upon thetype of material comprising the bumps 24. Alternatively, the bumps 24may be formed on the substrate 10 prior to attachment of the flip-chip.In other words, either surface may bear the bumps thereon. Althoughbumps 24 are typically formed with solder, it is understood that anyother materials known in the art (e.g. gold, indium, tin lead, silver oralloys thereof) that reflow to make electrical interconnects tosubstrate 10 can also be used. Additionally, the bumps 24 may be formedof conductive polymeric and epoxy materials and may include variousmetals being plated thereon.

After reflowing of the bumps 24, a space or gap 26 is formed between theactive surface 20 of flip-chip 12 and the top surface 18 of substrate10. The size of the gap 26 is controlled by the size of the reflowedsolder bumps and typically varies from approximately 3 to about 10 mils.

Next, an underfill material 28 is applied to fill the gap 26 between theflip-chip 12 and the substrate 10. As previously stated, the purpose ofthe underfill material 28 is to environmentally seal the active surface20 of the flip-chip 12 and the bumps 24, to help provide an additionalmechanical bond between the flip-chip 12 and the substrate 10 to helpprevent and/or distribute stress on the flip-chip 12 and bumps 24 and tohelp transfer heat from the flip-chip 12. The underfill material istypically a polymeric material, such as an epoxy or an acrylic resin,and may contain inert filler material therein. The underfill material 28typically has a thermal coefficient of expansion that approximates thatof the flip-chip 12 and/or the substrate 10 to help minimize stressplaced on either the flip-chip 12 or the substrate 10 during theoperation of the flip-chip caused by the heating of the underfillmaterial 28. To promote filling of the gap between the substrate 10 andflip-chip 12, the viscosity of the underfill material 28 is controlled,taking into account the flow characteristics of the underfill material,the material characteristics of the substrate 10, the materialcharacteristics of the flip-chip 12, and the size of the gap.

As shown, the underfill process is started by elevating or inclining thefront end 14 of the substrate 10 in order to position the substrate 10on an inclined plane 2 with respect to a horizontal plane 1. The angleof elevation or inclination of the inclined plane 2 and the attendantsubstrate 10 and flip-chip 12 is dependent on the viscosity or the rateof dispensing of the underfill material 28. The viscosity of theunderfill material 28 should be adjusted to allow facile flow of theunderfill material 28 but should be left low enough to readily preventthe flow of the underfill material 28 beyond the perimeter of theflip-chip 12. It should also be understood that the substrate 10 may beinclined by placing the substrate 10 on a support member 44, such as atilted table or conveyor belt, as is shown in FIG. 3 and furtherdescribed below. Alternately, the substrate 10 may be inclined byplacing the substrate 10 below a support member or horizontal plane 1 asdescribed hereinbelow.

Underfilling is accomplished by applying the underfill material 28 underthe front sidewall 30 of flip-chip 12 and allowing it to flow betweenthe flip-chip 12 and the substrate 10 and around the bumps 24. Theunderfill material 28 is applied with an underfill dispenser 34, such asa syringe having a suitable nozzle thereon or any other dispensing meansknown in the art.

As shown, since the substrate 10 having flip-chip 12 thereon is placedon an incline, in addition to any fluid pressure used to inject theunderfill material and any capillary action force acting on theunderfill material, a gravitational force also acts on the underfillmaterial, causing the underfill material 28 to readily flow from frontsidewall 30 toward rear sidewall 32. Due to the additional action of thegravitational force to that of the injection pressure and capillaryaction, air pockets, bubbles, and voids found within the underfillmaterial 28 are displaced by the denser underfill material 28 as itflows toward the rear sidewall 32 of flip-chip 12. The ability todisplace and the speed of displacement of the voids is dependent on theinclined angle of the substrate 10 having flip-chip 12 thereon, theviscosity of the underfill material 28, the injection rate of theunderfill material 28, and the uniformity of the injection of theunderfill material 28 into the gap between the substrate 10 and theflip-chip 12 to form a substantially uniform flow front of underfillinto and through the gap. If desired, the process of underfilling thegap may be repeated by inclining the substrate 10 in the oppositedirection and subsequently dispensing another amount of underfillmaterial 28 from an opposing side of the flip-chip 12 into the gap toimprove the uniformity of the underfill material 28 filling the gap.

After application of the underfill material 28, the material is curedeither by heat, ultraviolet light, radiation, or other suitable means inorder to form a solid mass.

Referring now to FIG. 2, a second embodiment of an interconnectedflip-chip 12 and substrate 10 is shown. As shown, a dam or barrier 40 isused on the top surface 18 to FIG. 2; of the substrate 10 to helpcontain the flow of the underfill from the gap at the rear sidewall 32of the flip-chip 12. Conventional molding equipment and techniques (e.g.pour molding, injection molding, adhesive bonding, etc.) can be used toform the dam 40 on the substrate 10. The dam 40 is typically formed fromany suitable epoxy resin material compatible with the substrate 10.

The dam 40 extends upwards from and is substantially perpendicular tothe top surface 18 of the substrate 10. As shown, the dam 40 may be seento lay substantially parallel and slightly aft the rear sidewall 32 toFIG. 2; of the flip-chip 12.

The dam 40 limits the expansion or gravitational flow of the underfillmaterial 28 beyond the position of the dam 40. During the underfillprocedure, the underfill material 28 coats and spreads out onto thesurfaces of the flip-chip 12 and substrate 10. The dam 40 prevents thespread of underfill material 28 beyond the rear sidewall 32 of theflip-chip 12 by means of surface tension.

Additionally, use of the dam 40 (as opposed to using no dam) permits useof lower viscosity underfill materials, if so desired, during theunderfill procedure. The underfill material may be easily controlled anda wider range of viscosities may be used by controlling the depth of thedam 40 and by controlling the width between the rear sidewall 32 of theflip-chip 12 and the dam 40. Use of the dam 40 also permits tilting thesubstrate 10 at a greater angle of elevation with respect to thehorizontal plane 1 in order to accelerate the underfill process or topermit the use of higher viscosity underfill materials should such aneed arise. Furthermore, if desired, a dam 40 may be used on all threesides of the flip-chip 12 located on the substrate 10 except the side ofthe flip-chip 12 from which the underfill material 28 is beingdispensed.

Referring to FIG. 3, a side view of a flip-chip 12 and substrate 10,interconnected via bumps 24, of a third embodiment of the invention isshown. The substrate 10 is inclined with respect to a horizontal plane 1by placing the substrate 10 onto a support member 44. Support member 44can be a tilt table, a tilted conveyor belt, or any other means ofsupport suitable for holding the substrate 10 of the present invention.Preferably, support member 44 can be positioned and locked at variousangles and can also be elevated or lowered from front to back as well asside to side.

Attached to the support member 44 is a vibrator 48. The vibrator 48facilitates and hastens the displacement of air pockets and voids by theunderfill material 28 during the previously described underfill process.The action of the vibrator 48 also permits the use of higher viscosityunderfill materials and/or permits underfilling with the support member44 positioned at a gradual slope.

Referring to FIG. 4, a top view of an interconnected solder-bumped 24flip-chip 12 and substrate 10 of a fourth embodiment of the presentinvention is shown similar to that of the second embodiment as shown inFIG. 2. However, this particular embodiment illustrates the use of twodams 40 and 40', which are oriented transversely with respect to oneanother. The two dams 40 and 40' lie in substantially parallelorientation with respect to two mutually perpendicular and abuttingsidewalls 50 and 52 of the flip-chip 12.

The method of this embodiment permits underfilling along two sidewalls54 and 56 simultaneously. Dams 40 and 40' prevent the spread andoverflow of underfill material 28 beyond sidewalls 50 and 52 of theflip-chip 12. The underfill material may be easily controlled and awider range of viscosities may be used by controlling the depth of thedams 40 and 40', by controlling the width between the sidewalls 50 and52 of the flip-chip 12 and the dams 40 and 40', and by controlling thedistance between the corners 60 and 60' of the dams 40 and 40'.

An alternative method comprises tilting the substrate 10 so as toelevate sidewall 54 and applying the underfill material 28 undersidewall 54 via the underfill dispenser 34'. The substrate 10 is thentilted so as to elevate sidewall 56 and the underfill material 28 isdispensed along sidewall 56 via underfill dispenser 34. This alternatingunderfill technique can be repeated until the underfill material 28 isfree of air pockets and voids.

Referring to FIG. 5, a cross-sectional view of an interconnectedsolder-bumped 24 flip-chip 12 and substrate 10 of a fifth embodiment ofthe present invention is shown midway through the underfill process. Inthis particular embodiment, the substrate 10 has a suitably shapedopening 60 situated near the center of the substrate 10 through whichunderfill material 28 can be applied via the underfill dispenser 34.Additionally, dams 40 and 40' located on each side of the flip-chip 12are molded or suitably attached to top surface 18 of the substrate 10,as described hereinbefore, being positioned to lay slightly beyond firstand second sidewalls, rear sidewall 32, and front sidewall 30,respectively. It should also be understood that other dams 40' (notshown) are located on the first and second lateral sidewalls of theflip-chip 12 to confine the underfill.

Referring to drawing FIG. 6, a cross-sectional view of an interconnectedsolder-bumped 24 flip-chip 12 and substrate 10 of a sixth embodiment ofthe present invention is shown midway through the underfill process. Inthis particular embodiment, the substrate 10 has a suitably shapedopening 60 situated near the center of the substrate 10 through whichunderfill material 28 can be applied via the underfill dispenser 34. Inthis instance, there is no dam used to confine the underfill material28. Additionally, if desired, the substrate 10 having flip-chip 12located thereon may be tilted in each direction to enhance the flow ofthe underfill material 28 in the gap 26 between the substrate 10 and theflip-chip 12 during the underfilling process.

Referring to drawing FIG. 7, a cross-sectional view of an interconnectedsolder-bumped 24 flip-chip 12 and substrate 10 of a seventh embodimentof the present invention is shown midway through the underfill process.In this particular embodiment, the substrate 10 has a suitably shapedopening 60 situated near the center of the substrate 10 through whichunderfill material 28 can be applied via the underfill dispenser 34.Additionally, dams 40 and 40' located on each side of the flip-chip 12are molded or suitably attached to top surface 18 of the substrate 10,as described hereinbefore, being positioned to lay slightly beyond firstand second sidewalls, rear sidewall 32, and front sidewall 30,respectively. It should also be understood that other dams 40' (notshown) are located on the first and second lateral sidewalls of theflip-chip 12 to confine the underfill. In this instance, the substrate10 having flip-chip 12 located thereon is inverted during the underfillprocess so that the underfill material 26 is dispensed through theopening 60 into the gap 28 between the substrate 10 and flip-chip 12. Asin the previous embodiments, the substrate 10 is located at an anglewith respect to horizontal plane 1, although located therebelow andinclined with respect thereto.

In operation, the present method is initiated by elevating or incliningfront end 14 of the substrate 10. As the underfill material 28 is added,in this case by means of an opening 60 through the substrate 10, theunderfill material 28 flows towards the dam 40 and fills the loweredportion of the gap 26 between the flip-chip 12 and the substrate 10. Thefront end 14 of the substrate 10 is then lowered and the rear end 32 ofthe substrate 10 is elevated. The backfill method is then repeated withthe underfill material 28 now flowing towards the dam 40' to completethe filing of the gap 26 between the flip-chip 12 and the substrate 10.The underfill material 28 is then cured, as previously described.Alternately, the underfill material 28 may be cured after the partialfilling of the gap between the substrate 10 and flip-chip 12, theremainder of the gap filled and subsequently cured.

While the present invention has been described in terms of certainmethods and embodiments, it is not so limited, and those of ordinaryskill in the art will readily recognize and appreciate that manyadditions, deletions and modifications to the embodiments describedherein may be made without departing from the scope of the invention ashereinafter claimed.

What is claimed is:
 1. A method of attaching a semiconductor device to asubstrate having a gap formed therebetween by applying an underfillmaterial thereto, said method comprising the steps of:connecting thesemiconductor device to the substrate; elevating one end of thesubstrate to position the substrate and the connected semiconductordevice on an inclined plane with respect to a horizontal plane; andapplying the underfill material to a portion of the gap between thesubstrate and the semiconductor device at an uppermost elevated side ofthe gap formed between the substrate and the semiconductor device.
 2. Amethod of attaching a semiconductor device to a substrate having a gapformed therebetween, said method comprising the steps of:providing asemiconductor device having front wall, rear wall, first lateralsidewall and second lateral sidewall; providing a substrate forreceiving the semiconductor device, said substrate having a front edge,a rear edge, first lateral edge, and second lateral edge; connecting thesemiconductor device to the substrate; elevating front edge of thesubstrate to position the substrate and the semiconductor deviceconnected thereto on an inclined plane with respect to a horizontalplane; and applying an underfill material to a portion of the gaplocated between the substrate and the semiconductor device substantiallyadjacent said front sidewall of the semiconductor device.
 3. The methodof claim 2, wherein the step of elevating said front edge of thesubstrate comprises:placing the substrate on a support structure andelevating at least one portion of said support structure.
 4. The methodof claim 2, further comprising the step of;providing a dam on thesubstrate at a point adjacent to said rear sidewall of the semiconductordevice after said step of connecting the semiconductor device to thesubstrate.
 5. The method of claim 4, wherein said dam comprises:a damextending substantially a portion of the height of the gap formedbetween the semiconductor device and the substrate.
 6. The method ofclaim 4, wherein said dam comprises:a dam extending substantially aportion of the height of the gap formed between the semiconductor deviceand the substrate, the dam extending along substantially the firstlateral sidewall, second lateral sidewall, and rear wall of thesemiconductor device.
 7. The method of claim 2, further comprising thestep of:vibrating the substrate to agitate the underfill material. 8.The method of claim 7, wherein the step of vibrating the substratecomprises:placing the substrate on a support structure and vibratingsaid support structure.
 9. The method of claim 2, further comprising thesteps of:elevating the first lateral edge of the substrate to positionthe substrate on another inclined plane; and placing an underfillmaterial between the substrate and the semiconductor devicesubstantially under the first lateral sidewall of the semiconductordevice.
 10. The method of claim 9, further comprising the stepsof:elevating said front edge of the substrate; placing an underfillmaterial substantially under said front wall of the semiconductordevice; elevating the rear edge of the substrate; and placing anunderfill material substantially under the rear wall of thesemiconductor device.
 11. The method of claim 9, further comprising thestep of:providing a dam on the substrate at a point adjacent to thefirst lateral sidewall of the semiconductor device to inhibit saidunderfill material from substantially spreading beyond the first lateralsidewall of the semiconductor device.
 12. The method of claim 11,further comprising the step of:providing a dam on the substrate at apoint adjacent to the first lateral sidewall, second lateral sidewall,and rear wall of the semiconductor device to inhibit said underfillmaterial from substantially spreading therebeyond.
 13. The method ofclaim 11, further comprising the step of:elevating the first lateraledge of the substrate.
 14. The method of claim 9, further comprising thestep of:vibrating the substrate to agitate said underfill material. 15.The method of claim 2 wherein the step of connecting the semiconductordevice to the substrate comprises the steps of;depositing solder uponthe semiconductor device; and attaching the semiconductor device on thesubstrate to form an electrical and mechanical connection therebetween.16. The method of claim 2, wherein the step of providing a semiconductordevice comprises:attaching a bumped die to the substrate thereby forminga gap between the bumped die and the substrate.
 17. The method of claim2, wherein the step of providing a semiconductor devicecomprises:attaching a semiconductor device to a printed circuit board.18. A method of attaching a bumped die to a printed circuit board, saidmethod comprising the steps of:providing a bumped die having a frontsidewall and a rear sidewall, said rear sidewall being opposite to saidfront sidewall; providing a printed circuit board for receiving thebumped die, said printed circuit board having a front end facing saidfront sidewall of the bumped die and a rear end facing said rearsidewall of the bumped die; electrically connecting the bumped die tothe printed circuit board; providing a dam on the printed circuit boardat a point adjacent to said rear sidewall of the bumped die to preventsaid underfill material from spreading beyond said rear sidewall of thebumped die; elevating said front end of the printed circuit board toposition the printed circuit board on an inclined plane; and applying anunderfill material between the printed circuit board and the bumped diesubstantially under said front sidewall of the bumped die.
 19. A methodof substantially sealing a gap formed between a semiconductor device anda substrate by applying an underfill material thereto, said methodcomprising the steps of:attaching the semiconductor device to thesubstrate; elevating one end of the substrate to position the substrateand the connected semiconductor device on an inclined plane with respectto a horizontal plane; and applying the underfill material to a portionof the gap between the substrate and the semiconductor device at anuppermost elevated side of the gap formed between the substrate and thesemiconductor device.
 20. A method of substantially sealing a gap formedbetween a semiconductor device and a substrate, said method comprisingthe steps of:providing a semiconductor device having a front wall, rearwall, first lateral sidewall and second lateral sidewall; providing asubstrate for receiving the semiconductor device, said substrate havinga front edge, a rear edge, first lateral edge, and second lateral edge;attaching the semiconductor device to the substrate; elevating the frontedge of the substrate to position the substrate and the semiconductordevice connected thereto on an inclined plane with respect to ahorizontal plane; and applying an underfill material to a portion of thegap located between the substrate and the semiconductor devicesubstantially adjacent said front sidewall of the semiconductor device.21. A method of substantially sealing a gap formed between a bumped dieand a printed circuit board, said method comprising the stepsof:providing a bumped die having a front sidewall and a rear sidewall,said rear sidewall being opposite to said front sidewall; providing aprinted circuit board for receiving the bumped die, said printed circuitboard having a front end facing said front sidewall of the bumped dieand a rear end facing said rear sidewall of the bumped die; attachingthe bumped die to the printed circuit board; providing a dam on theprinted circuit board at a point adjacent to said rear sidewall of thebumped die to substantially inhibit the flow of said underfill material;elevating said front end of the printed circuit board to position theprinted circuit board on an inclined plane; and applying an underfillmaterial to a portion of the gap formed between the printed circuitboard and the bumped die substantially under said front sidewall of thebumped die.
 22. A method of substantially sealing a gap formed between asemiconductor device and a substrate, said method comprising the stepsof:attaching the semiconductor device to the substrate; inclining oneend of the substrate to position the substrate and the connectedsemiconductor device on an inclined plane with respect to a horizontalplane; and applying an underfill material to a portion of the gap formedbetween the substrate and the semiconductor device at an uppermostinclined side of the substrate and the semiconductor device.
 23. Amethod of substantially sealing a gap formed between a semiconductordevice and a substrate, said method comprising the steps of:providing asemiconductor device having front wall, rearwall first lateral sidewalland second lateral sidewall; attaching the semiconductor device to thesubstrate; inclining the front edge of the substrate to position thesubstrate and the semiconductor device connected thereto on an inclinedplane with respect to a horizontal plane; and applying an underfillmaterial to a portion of the gap formed between the substrate and thesemiconductor device substantially adjacent said front sidewall of thesemiconductor device.
 24. A method of substantially sealing a gap formedbetween a bumped die and a printed circuit board, said method comprisingthe steps of:providing a bumped die having a front sidewall and a rearsidewall, said rear sidewall being opposite to said front sidewall;providing a printed circuit board for receiving the bumped die, saidprinted circuit board having a front end facing said front sidewall ofthe bumped die; attaching the bumped die to the printed circuit board;providing a dam on the printed circuit board at a point adjacent to saidrear sidewall of the bumped die to substantially inhibit the flow ofsaid underfill material from spreading beyond said rear sidewall of thebumped die; inclining said front end of the printed circuit board toposition the printed circuit board on an inclined plane; and applying anunderfill material to a portion of the gap formed between the printedcircuit board and the bumped die substantially under said front sidewallof the bumped die.
 25. A method of substantially sealing a gap formedbetween a semiconductor device and a substrate and substantiallyattaching a portion of said semiconductor device to a portion of saidsubstrate by applying an underfill material thereto, said methodcomprising the steps of:attaching the semiconductor device to thesubstrate; elevating one end of the substrate to position the substrateand the connected semiconductor device on an inclined plane with respectto a horizontal plane; and applying the underfill material to a portionof the gap between the substrate and the semiconductor device at anuppermost elevated side of the gap formed between the substrate and thesemiconductor device.
 26. A method of substantially sealing a gap formedbetween a semiconductor device and a substrate and substantiallyattaching a portion of said semiconductor device to a portion of saidsubstrate, said method comprising the steps of:providing a semiconductordevice having a front wall, rear wall, first lateral sidewall and secondlateral sidewall; providing a substrate for receiving the semiconductordevice, said substrate having a front edge, a rear edge, first lateraledge, and second lateral edge; attaching the semiconductor device to thesubstrate; elevating the front edge of the substrate to position thesubstrate and the semiconductor device connected thereto on an inclinedplane with respect to a horizontal plane; and applying an underfillmaterial to a portion of the gap located between the substrate and thesemiconductor device substantially adjacent said front sidewall of thesemiconductor device.
 27. A method of substantially sealing a gap formedbetween a bumped die and a printed circuit board and substantiallyattaching a portion of said bumped die to a portion of said printedcircuit board, said method comprising the steps of:providing a bumpeddie having a front sidewall and a rear sidewall, said rear sidewallbeing opposite to said front sidewall; providing a printed circuit boardfor receiving the bumped die, said printed circuit board having a frontend facing said front sidewall of the bumped die and a rear end facingsaid rear sidewall of the bumped die; attaching the bumped die to theprinted circuit board; providing a dam on the printed circuit board at apoint adjacent to said rear sidewall of the bumped die to prevent saidunderfill material from spreading beyond said sidewall of the bumpeddie; elevating said front end of the printed circuit board to positionthe printed circuit board on an inclined plane; and applying anunderfill material to a portion of the gap formed between the printedcircuit board and the bumped die substantially under said front sidewallof the bumped die.
 28. A method of substantially sealing a gap formedbetween a semiconductor device and a substrate and substantiallyattaching a portion of said semiconductor device to a portion of saidsubstrate, said method comprising the steps of:attaching thesemiconductor device to the substrate; inclining one end of thesubstrate to position the substrate and the connected semiconductordevice on an inclined plane with respect to a horizontal plane; andapplying an underfill material to a portion of the gap formed betweenthe substrate and the semiconductor device at an uppermost inclined sideof the substrate and the semiconductor device.
 29. A method ofsubstantially sealing a gap formed between a semiconductor device and asubstrate and substantially attaching a portion of said semiconductordevice to said substrate, said method comprising the steps of:providinga semiconductor device having front wall, rearwall first lateralsidewall and second lateral sidewall; attaching the semiconductor deviceto the substrate; inclining the front edge of the substrate to positionthe substrate and the semiconductor device connected thereto on aninclined plane with respect to a horizontal plane; and applying anunderfill material to a portion of the gap formed between the substrateand the semiconductor device substantially adjacent said front sidewallof the semiconductor device.
 30. A method of substantially sealing a gapformed between a bumped die and a printed circuit board andsubstantially attaching a portion of said bumped die to a portion ofsaid printed circuit board, said method comprising the stepsof:providing a bumped die having a front sidewall and a rear sidewall,said rear sidewall being opposite to said front sidewall; providing aprinted circuit board for receiving the bumped die, said printed circuitboard having a front end facing said front sidewall of the bumped die;attaching the bumped die to the printed circuit board; providing a damon the printed circuit board at a point adjacent to said rear sidewallof the bumped die to prevent said underfill material from spreadingbeyond said rear sidewall of the bumped die; inclining said front end ofthe printed circuit board to position the printed circuit board on aninclined plane; and applying an underfill material to a portion of thegap formed between the printed circuit board and the bumped diesubstantially under said front sidewall of the bumped die.
 31. A methodof substantially underfilling a gap formed between a semiconductordevice and a substrate by applying an underfill material thereto, saidmethod comprising the steps of:attaching the semiconductor device to thesubstrate; elevating one end of the substrate to position the substrateand the connected semiconductor device on an inclined plane with respectto a horizontal plane; and applying the underfill material to a portionof the gap between the substrate and the semiconductor device at anuppermost elevated side of the gap formed between the substrate and thesemiconductor device.
 32. A method of substantially underfilling a gapformed between a semiconductor device and a substrate, said methodcomprising the steps of:providing a semiconductor device having a frontwall, rear wall, first lateral sidewall and second lateral sidewall;providing a substrate for receiving the semiconductor device, saidsubstrate having a front edge, a rear edge, a first lateral edge, and asecond lateral edge; attaching the semiconductor device to thesubstrate; elevating the front edge of the substrate to position thesubstrate and the semiconductor device connected thereto on an inclinedplane with respect to a horizontal plane; and applying an underfillmaterial to a portion of the gap located between the substrate and thesemiconductor device substantially adjacent said front sidewall of thesemiconductor device.
 33. A method of substantially underfilling a gapformed between a bumped die and a printed circuit board, said methodcomprising the steps of:providing a bumped die having a front sidewalland a rear sidewall, said rear sidewall being opposite to said frontsidewall; providing a printed circuit board for receiving the bumpeddie, said printed circuit board having a front end facing said frontsidewall of the bumped die and a rear end facing said rear sidewall ofthe bumped die; attaching the bumped die to the printed circuit board;providing a dam on the printed circuit board at a point adjacent to saidrear sidewall of the bumped die to prevent said underfill material fromspreading beyond said sidewall of the bumped die; elevating said frontend of the printed circuit board to position the printed circuit boardon an inclined plane; and applying an underfill material to a portion ofthe gap formed between the printed circuit board and the bumped diesubstantially under said front sidewall of the bumped die.
 34. A methodof substantially underfilling a gap formed between a semiconductordevice and a substrate, said method comprising the steps of:attachingthe semiconductor device to the substrate; inclining one end of thesubstrate to position the substrate and the connected semiconductordevice on an inclined plane with respect to a horizontal plane; andapplying an underfill material to a portion of the gap formed betweenthe substrate and the semiconductor device at an uppermost inclined sideof the substrate and the semiconductor device.
 35. A method ofsubstantially underfilling a gap formed between a semiconductor deviceand a substrate, said method comprising the steps of:providing asemiconductor device having a front wall, a rear wall, a first lateralsidewall and a second lateral sidewall; attaching the semiconductordevice to the substrate; inclining the front edge of the substrate toposition the substrate and the semiconductor device connected thereto onan inclined plane with respect to a horizontal plane; and applying anunderfill material to a portion of the gap formed between the substrateand the semiconductor device substantially adjacent said front sidewallof the semiconductor device.
 36. A method of substantially underfillinga gap formed between a bumped die and a printed circuit board, saidmethod comprising the steps of:providing a bumped die having a frontsidewall and a rear sidewall, said rear sidewall being opposite to saidfront sidewall; providing a printed circuit board for receiving thebumped die, said printed circuit board having a front end facing saidfront sidewall of the bumped die; attaching the bumped die to theprinted circuit board; providing a dam on the printed circuit board at apoint adjacent to said rear sidewall of the bumped die to prevent saidunderfill material from spreading beyond said rear sidewall of thebumped die; inclining said front end of the printed circuit board toposition the printed circuit board on an inclined plane; and applying anunderfill material to a portion of the gap formed between the printedcircuit board and the bumped die substantially under said front sidewallof the bumped die.